Both multidetector row computed tomography (MDCT) and magnetic resonance imaging (MRI) are used to evaluate the bladder noninvasively. MDCT Offers fast imaging with near-isotropic data sets optimized for three-dimensional imaging, including the latest software for volume rendering. MRI provides distinctive soft tissue contrast resolution and can perform dynamic imaging without radiation exposure. This article discusses the techniques and protocols of each modality with case illustrations of their application in a range of bladder pathologies to show their respective distinct advantages and limitations.
Patient preparation for multidetector row computed tomography (MDCT) and magnetic resonance imaging (MRI) involves supine positioning with alternate positions to displace bowel loops or bladder contrast. Moderate distention is preferred to display wall contrast and filling defects better and to improve specificity for true wall thickening. For a dedicated urine-filled bladder study, the patient voids 2-3 hours before the examination. A Foley catheter may be placed for direct bladder distention for optimal image quality, and if one is already present, it should be clamped. It is important not to catheterize the bladder before imaging if detection of air from an enterovesical fistula is a consideration.
To differentiate bowel from bladder, positive contrast is used for routine computed tomography (CT) and neutral contrast (water) is preferred for three-dimensional postprocessing. Rectal contrast is used occasionally, especially when tissue planes of the pelvis have been disrupted. Intramuscular glucagon (1 mg) is used to diminish movement artifact on MRI. Peripheral vein access is obtained for contrast-enhanced studies.
For MRI, body coils suffice for upper abdominal ret-roperitoneal and liver imaging and double-phased array surface pelvic coils provide a small field of view and improve signal-to-noise ratio.23 A waist compression belt may help to limit abdominal wall motion artifact for MRI.